The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent that it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Spark ignition direct injection (SIDI) engines have improved fuel economy and increased power over conventional port fuel-injected combustion engines. A fuel injection system for an SIDI engine is operated at high pressure to spray fuel directly into combustion chambers. A fuel pump for supplying the fuel to a fuel rail at high pressure may be mechanically driven by the engine. During engine cold start, the engine may not have sufficient power to drive the fuel pump to generate the desired high pressure. Further, the engine generally requires a richer air/fuel mixture at cold start to maintain constant speeds and thus requires even higher fuel pressure. The fuel pump of the SIDI engine may not be able to meet the fuel demand at engine cold start. A fuel pump with a larger capacity may improve performance of the SIDI engine at cold start while increasing manufacturing costs of the engine.